PhD Candidate Talks About the Physics of Space Battles

darthvader100 writes "Gizmodo has run an article with some predictions on what future space battles will be like. The author brings up several theories on propulsion (and orbits), weapons (explosives, kinetic and laser), and design. Sounds like the ideal shape for spaceships will be spherical, like the one in the Hitchhiker's Guide movie."

Round ships?

[Duhavid]

"Sounds like the ideal shape for spaceships will be spherical, like the one in the Hitchhiker's Guide movie"

Or maybe like Doc Smith predicted in the Lensman Series?

Re:Round ships?

[JonStewartMill]

Or the jacket illustrator [wikipedia.org] for at least one of Robert Heinlein's 'juvies'?

Okay, so it's actually lightbulb-shaped. Close enough.

Re:C.J. Cherryh has the most realistic handling

[maxume]

Do you mean Stephen Donaldson?

I'm reasonably familiar with Stephenson's work and do not recognize his 'Gap series'.

Article and grandparent are just wrong.

[RightSaidFred99]

They would be useful. Article is simply wrong. Sure, you don't have the shockwave but that much pure energy (even just the part that's shipward) would do a whole shitload of damage. You detonate the nuke when it hits the ship, I mean physically touches the ship. The ship will be destroyed. It's not like a ground based nuke where most damage comes from detonating in the air.

Heinlein

[Garrett Fox]

Sounds like the premise of Heinlein's "The Moon Is a Harsh Mistress". Revolutionaries on the Moon take control of a mass driver and start flinging multi-ton barges at Earth, with just enough remote-control maneuvering that the shooters can call up Earth afterward and ask if they'd like to surrender.

Re:C.J. Cherryh has the most realistic handling

[Astronomerguy]

Just a minor correction: the "Gap..." series was authored by Stephen R. Donaldson. http://www.stephenrdonaldson.com/ [stephenrdonaldson.com]

Re:Nukes in Space. . .

[idontgno]

Those gamma and X-rays are bad news when absorbed by stuff like a spacecraft hull. The photon flux is so high that even transparent substances like air absorb ghastly amounts of those. That's the source of the atmospheric shock from a nuke, and the source of the distinctive thermal double-flash: initial infrared pulse, occluded after a few nanoseconds by the atmosphere flashing into opaque plasma, and the resuming after the shockwave begins to dissipate the opacity. Any substance more opaque than air will just immediately flash to plasma and create its own shockwave in the rest of the target.

Yes, the inverse-square law applies to the photon burst from a nuke in space, so a nuke is not the large-area weapon it is in atmosphere. But to write off the huge pulse of ionizing radiation is mistaken. A contact or near-contact nuke would hurt bad.

A perfect x-ray laser would be immune to the inverse-square law, but a perfect laser doesn't exist. Every real-world laser will have a divergence angle; that would give the beam with an inverse-square behavior with a constant coefficient based on the ratio of the divergence angle as a solid angle [wikipedia.org] and the solid angle of a unit sphere (4 pi).

Re:Article and grandparent are just wrong.

[Rei]

That is absolutely correct. The author seems to be unfamiliar with just how devastatingly destructive nuclear weapons are in space.

First, re. the airblast: the reason nuclear weapons have an airblast on earth is that the X-rays from the explosion are so intense that they superheat every piece of atmosphere (and ground, and ocean, and so forth) around the explosion, leading to rapid expansion. So if the detonation is near the ship, the ship itself will become just as superheated as the air that turns into the airblast on Earth. More, actually, because there's nothing to get in the way of the X-rays from the explosion.

Furthermore, the lethal range of the radiation from nuclear weapons in space is tremendously large -- many hundreds, if not thousands, of miles. While a kinetic kill vehicle has to actually hit you, a nuclear explosion doesn't have to be even close. And some of it may actually turn your kinetic shielding against you -- for example, bremsstrahlung [wikipedia.org].

Re:Article and grandparent are just wrong.

[Lehk228]

you are misunderstanding just how huge space is, docking ships in orbit is tricky and that is on an orbit not a full unrestricted 3D volume of space, and that is with the other craft cooperating.

trying to get a missile to do it at speeds fast enough to be useful, while sorting spoofed emissions from electronic warfare drones and dodging point defense lasers, all while too far away for your ships computers and sensors to do much good.

Re:round round, I git around

[Arthur Grumbine]

Seen from the front though the rectangle only presents a profile of 100. The maximum profile it will exhibit is 1000, and thats only directly from the side. The sphere, if I'm not mistaken, will always present in the region of 1800.

You are mistaken. 3,694/6 = ~616. Note also that the claim of the GP was specifically in regards to multiple opponents able to move around you a in 3-dimensional battleground. Sure, you could always keep your nose/tail oriented at the most dangerous threat, and when only facing two threats (and assuming perfect piloting) you can reduce your total profile available to your opponents to 1100 (assuming you're opponents are at least bright enough to attack from complementary vectors), which is less than the 1232 that the sphere would present to the two opponents. But as soon as you're dealing with more than three opponents/potential-attack-vectors, you're worse off.